• The Journal of Korea Robotics Society
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• v.5 no.4
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• pp.349-358
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• 2010

We presents a dynamic modeling of 4-wheel 2-DOF. WMR. The classic dynamic model utilizes a greatly simplified wheel motion representation and using of a simplified dynamic model confronts with a problem for accurate position control of wheeled mobile robot. In this paper, we treats the dynamic model for describes relationship between the wheel actuator force/torque and WMR motion through the use of Newton's equilibrium laws. To calculate the WMR position in real time, we introduced the Dead-Reckoning algorithms and the simulation result show that the proposed dynamic model is useful. We can be easily extend the proposed WMR model to mobile robot of similar type and this type of methodology is useful to analyze, design and control any kinds of rolling robots.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.793-799
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• 2011

A comprehensive analysis of wheel force spectrum is conducted to provide the KTX safety evaluation with structural behaviour of Pre-Stressed Concrete (PSC) box bridge due to various high speeds. The wheel spectrum for KTX locomotive running over road and PSC bridge tracks is compared using irregular track responses with numerical models of 170m approach road track and 40m span length of PSC box bridge The high-speed railway locomotive is used as 38-degree of freedom system. Three displacements (vertical, lateral, and longitudinal) and three rotational components (pitching, rolling, and yawing) for one car-body and two bogies are considered in the 38-degree of freedom model. Three dimensional frame element of finite element method (FEM) is used to model of the simply supported PSC box bridge. The irregulation of rail-way is derived using the experiential spectrum density function under assumption of twelve level tracks conditions based on the normal probability procedure. The dynamic analyses by Runge-Kutta method which are able to analyze the high frequency wheel force spectrum. A dynamic behaviour of KTX due to high speeds until 450km/h developing speed with relative time is analysed and compared the characteristics running over the road and PSC box bridge tracks. Finally, the KTX integrated evaluation method of safety between high speed train and bridge is presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.151-162
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• 1998

During a straight driving and cornering maneuver by a vehicle various forces and moments are exerted on the tire's footprint. A cornering properties, handling and stability performances of vehicle can be predicted by these forces and moments values. Therefore, on this study, a lateral force and a aligning torque are predicted by these forces and moments values. Therefore, on this study, a lateral force and a aligning torque are predicted using a finite element method. Contact area of the tire between bead and wheel are fixed to simplify of a finite element model. Lateral force is exerted on the rigid surface as a real load with Coulum friction after inflate and load vertically. Then, rotate the tire's axle to simulate a free rolling untill taken the equilibrium of a aligning torque. Also, experimental observations are made to test a reliability of a FE analysis conducted in this study. The finite element analysis said that good agreement was obtained with experimental results of these cornering properties, giving confidence within about one percent. So it os recommended that a finite element analysis can be used as a good tool to predicted the tire cornering properties.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.297-303
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• 2001

This research presents an analytical model to characterize the ball bearing vibration due to the waviness in a rigid rotor supported by multi-row ball bearings considering centrifugal force and gyroscopic moment of ball. The effects of centrifugal force and gyroscopic moment are introduced to the kinematic constraints and force equilibrium equations. The waviness of ball and races is modeled by the superposition of sinusoidal function and it is introduced to position vectors of race curvature center to use the Hertzian contact theory in order to calculate the elastic deflection and nonlinear contact force resulting from the waviness while the rotor has translational and angular motion. They can be determined by solving the nonlinear equations of motion with five degrees of freedom by using the Runge-Kutta-Fehlberg algorithm. The accuracy of this research is validated by comparing with the results of the prior researches. It characterizes the vibration frequencies resulting from the various kinds of waviness in rolling elements, the harmonic frequencies resulting from the nonlinear load-deflection characteristics of ball bearing resulting from the waviness interaction.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.233-237
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• 2009

In this study, we suggest that several approaches to evaluate the collision acceleration value of a car in the article 35 and the guideline 16 of Korean rolling stock safety regulation. There are various methods to evaluate collision acceleration such as; a displacement comparison method by the double integration of filtered acceleration data, a velocity comparison method by the integration of filtered acceleration data, an analysis method of time-velocity curve, or a differential method of time-velocity curve. We compared these methods one another using 1D dynamic simulation model composed of nonlinear dampers, springs and bars, and masses. Also, we applied these methods to a hybrid model, which is made of 3D shell element model and 2D collision dynamics model, in order to evaluate whether 1D force-displacement curve modeling for energy absorbing structures have an effect on the collision acceleration levels or not.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.504-509
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• 2005

Railway noise and vibration has been recognized as major problems with the speed-up of rolling stock. As a kind of solution to these problems, the decrease of stiffness of track pad have been tried. However, in this case, overturning of rail due to lateral force should be considered because it can have effect on the safety of running train. Therefore, above two things - decrease of stiffness of track pad and overturning of rail due to lateral force - should be considered simultaneously for the appropriate determination of spring coefficient of track pad. With this viewpoint, minimum spring coefficient of track pad is estimated through the comparison between the theoretical relationship about the overturning of rail and 3-dimensional FE analysis result. Two kinds of Lateral force and wheel load are used as input loads. Extracted values from the conventional estimation formula and the Shinkansen design loads are used. It is found that the overturning of rail changes corresponding to the change of the stiffness of track pad and the ratio of lateral force to wheel load. Moreover, it is found that the analysis model can have influence on the results. Through these procedure, minimum spring coefficient of track pad is estimated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.135-136
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• 2006

A precise linear motion stage supported by magnetically preloaded air bearings is introduced where preloading magnetic actuators are combined with permanent magnets and coils to adjust air bearing clearance by controlling magnetic force actively. Each of the magnetic actuators has a permanent magnet generating nominal magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air-bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate nominal preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder is built for verifying this design concept. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed, and the result shows very good linearity.

• Journal of Ocean Engineering and Technology
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• v.30 no.1
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• pp.18-24
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• 2016

Stabilizer fins are installed on each side of a ship to control its roll motion. The most common stabilizer fin is a rolling control system that uses the lift force on the fin surface. If the angle of attack of a stabilizer fin is zero or the speed is zero, it cannot control the roll motion. The Coanda effect is well known to generate lift force in marine field. The performance of stabilizer fin that applies the Coanda effect has been verified by model tests and numerical simulations. It was found that a stabilizer fin that applied the Coanda effect at Cj = 0.085 and a zero angle of attack exactly coincided with that of the original fin at α = 26°. In addition, the power needed to generate the Coanda effect was not high compared to the motor power of the original stabilizer fin.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.621-633
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• 2006

To reflect the size effect of material $(1\sim15{\mu}m)$ during plastic deformation of polycrystalline copper, a constitutive equation which includes the strain gradient plasticity theory and intrinsic material length model is coupled with the finite element analysis and applied to plane strain deformation problem. The method of least square has been used to calculate the strain gradient at each element during deformation and the effect of distributed force on the strain gradient is investigated as well. It shows when material size is less than the intrinsic material length $(1.54{\mu}m)$, its deformation behavior is quite different compared with that computed from the conventional plasticity. The generation of strain gradient is greatly suppressed, but it appears again as the material size increases. Results also reveal that the strain gradient leads to deformation hardening. The distributed force plays a role to amplify the strain gradient distribution.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.223-230
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• 2004

In this paper, we will introduce a control strategy based on the permanent magnet linear synchronous motor (PMLSM) container transfer system using soft-computing algorithm. Linear motor-based container transport system (LMCTS) is horizontal transfer system for the yard automation, which has been proposed to take the place of automated guided vehicle in the maritime container terminal. LMCTS is considered as that the system is changed its model suddenly and variously by loading and unloading container. The proposed control system is consisted of two DR-FNNs that act the role of controller and system emulator. Consequently, the system had the predictable structure and an ability to adapt for a huge variation of rolling friction, detent force, and sudden changes of its weight by loading and unloading.